Method of making beryllium-aluminum wrought material

ABSTRACT

A method of producing wrought material containing beryllium and aluminum comprising: forming a casting of said material in a mold having high thermal conductivity material; applying a protective coating to said casting; heating the coated casting at a temperature of 700* to 1,100* F for a period of 5 to 100 hours; extruding the heated casting at a rate of about 13 to 60 inches per minute; removing the jacket from the extruded casting; heating the extrusion at a temperature of 900* to 1,150* F for a period of time of 12 hours to 1 week; and rolling the heated extrusion at a total reduction of 10 to 98%.

[451 Apr. 25, 1972 METHOD OF MAKING BERYLLIUM- ALUMINUM WROUGHT MATERIAL Inventors: Richard H. Krock, Weston; William J.

Richmond, Reading, both of Mass.

P. R. Mallory & Co. Inc., Indianapolis, Ind.

Filed: July 17, 1970 App1.No.: 55,687

Assignee:

U.S. Cl. ..29/527.7, 29/193, 29/DlG. 32, 29/D1G. 47, 148/2, 164/76 Int. Cl ..B23k 19/00 Field of Search ..29/527.7, DIG. 32, DlG.47, 29/193; 75/150; 148/2; 164/76 References Cited UNITED STATES PATENTS 3,558,305 1/1971 Griffiths ..75/l50 OTHER PUBLICATIONS Forming of Beryllium," Metals Handbook, Eighth Edition, Volume 4, pp. 402- 405, c. 1969.

Primary Examiner-John F. Campbell Assistant Examiner- Donald C. Reiley, lll Attorney-Richard H. Childress, Robert F. Meyer and Henry W. Cummings 57] ABSTRACT A method of producing wrought material containing beryllium and aluminum comprising: forming a casting of said material in a mold having high thermal conductivity material; applying a protective coating to said casting; heating the coated casting at a temperature of 700 to 1,l00 F for a period of 5 to 100 hours; extruding the heated casting at a rate of about 13 to 60 inches per minute; removing the jacket from the extruded casting; heating the extrusion at a temperature of 900 to 1,150 F for a period oftime of 12 hours to 1 week; and rolling the heated extrusion at a total reduction of 10 to 98%.

22 Claims, 5 Drawing Figures PATENTEDAPRZS I972 FIG fl 23' FINE. 5

INVENTORS RICHARD H KROCK WILLIAM J. RICHMOND M ATTORNEY METHOD OF MAKING BERYLLIUM-ALUMINUM WROUGHT MATERIAL Previous attempts at preparing wrought products i.e. sheet, plate, rod, bar, made of beryllium-aluminum alloy have not been successful on a commercial basis because of the relatively brittle nature of the alloy. This brittleness to date has made working the material very difficult.

In U.S. Pat. application, Ser. No. 873,635, filed Nov. 3, 1969, now abandoned assigned to the same assignee as the present application, a process of refining the microstructure of beryllium-aluminum alloys is disclosed involving forming castings of beryllium-aluminum alloy; attaching the castings to an electrode; partly melting the electrode while rotating the same, thereby causing droplets to fly from the electrode; and cooling the droplets to form particulate beryllium-aluminum material with a fine grain structure.

While this process is successful in refining the grain structure and reducing the brittle nature of the material, the formation of wrought products by rolling or extruding has still been difficult even with this refined grain structure.

It is an object of the present invention to provide wrought products from beryllium-aluminum material.

It is the object of the present invention to provide a process for providing beryllium-aluminum sheet material.

It is the object of the present invention to provide a process for providing beryllium-aluminum plate material.

It is the object of the present invention to provide a process for providing beryllium-aluminum rod material.

It is the object of the present invention to provide a process for providing beryllium-aluminum bar material.

It is the object of the present invention to provide berylliumaluminum wrought material with increased elongation.

It is another object of the present invention to provide beryllium-aluminum wrought material which has substantially the same properties in the transverse direction as in the longitudinal direction.

It is another object of the present invention to provide a process which does not require the use of an intermediate matrix refinement step.

It is another object of the present invention to provide a process which is suited to commercial use on conventional equipment.

Other objects will be apparent from the following description and drawings.

FIG. 1 is a sectional view and FIG. 2 an end view of an evacuation jacket which can be utilized in the present invention.

FIG. 3 is a front view, FIG. 4 a top view, and FIG. 5 a side view of extrusion dies which may be utilized in the present invention.

The alloy composition to be utilized in accordance with the present invention consists essentially of beryllium in an amount of about 60 to about 85% by weight and aluminum 14 to about 40% by weight. Impurities are preferably each not greater than about 0. l total not greater than about 1%.

The preferred composition consists essentially of about 70 to about 80% by weight beryllium and about to about by weight aluminum.

The first step in the process is to form castings of this alloy composition. The method of casting may involve the use of an alkali or alkaline earth halide flux as described in application, Ser. No. 667,910, filed Sept. I5, 1967, now U.S. Pat. No. 3,558,305. Alternatively, the casting may be formed in accordance with application, Ser. No. 832,439, filed June ll, 1969, now Pat. No. 3,548,915, wherein the melting chamber is first evacuated and then back filled with an inert gas prior to casting. Both of these applications, as well as the said application, Ser. No. 873,635, are hereby incorporated into the present application by reference and expressly made a part hereof.

A third method of forming the casting is to form a casting in the shape of a consumable electrode by any known method, for instance by either of the methods as described in said U.S.

Pat. No. 3,558,305 or U.S. Pat. No. 3,548,915, and then use this casting as a consumable arc electrode in a consumable arc casting process. In consumable arc casting a DC voltage is employed between the consumable electrode and the casting and an arc is struck therebetween. For example, the voltage utilized is from about 40 to about volts and the current about 400 to 800 amps. The mold must be made of a material which is highly thermally and electrically conductive. Non-limiting examples of such materials are copper, copper alloys and graphite. Copper and copper alloys are preferred.

In the event that the casting process is carried out according to U.S. Pat. No. 3,558,305 and/or U.S. Pat. No. 3,548,915, the preferred mold material is a highly thermally conductive material. Among the mold materials which may be used are: graphite, copper or copper alloys, iron or steel.

In general the mold will be liquid i.e. water, cooled but air cooling may also be utilized where a less rapid cooling rate can be tolerated. Air cooling usually results in a less fine microstructure in comparable casting section sizes. The smallest cross sectional dimension in the casting may be up to 6 inches and higher, but preferably the smallest dimension is below about 3 inches.

The mold is preferably shaped so that the casting is of cylindrical shape. However, square and rectangular castings can also be utilized in the process as well as eliptical and hyperbol- 'ic cross sections. The casting may be of any desired length;

however, for casting convenience the casting is usually not longer than 6 feet.

The next step is to clean up the castings to remove surface imperfections in the castings. This is preferably done by machining, for example on a conventional lathe having a conventional machining tool i.e. tungsten carbide/cobalt. Machining lathes of this type are conventional and the lathe per se and its cutting tool form no part of this invention. The machining operation also is utilized to get the castings to tolerances as close to the desired shape as practical. Exemplary dimensional tolerances are :3 to 1-10 thousandths. If the casting is sufficiently close to tolerance and sufficiently free of surface imperfections the machining step may be eliminated.

After the machining operation a layer of protective metal is applied to the casting. This material must have high thermal conductivity; be sufiiciently strong to withstand extrusion pressures and sufficiently ductile to flow. A relatively high melting point about above l,000 C is preferred. Silver, gold and their alloys may be used but copper and copper alloys i.e. brass, bronze, are preferred. This layer can be applied by placing the castings in a jacket of protective metal or by applying a coating of protective metal for example by plating. If the casting is placed in a jacket, the jacket preferably is of slightly larger size, for example of 10 to 20 thousandths of an inch larger.

In the event that a plating solution is employed conventional plating solutions may be utilized for this purpose including for example cyanide, sulphate, and halide as the negative ion in solution.

The preferred procedure is to place the casting in the metal jacket, preferably copper, having an evacuation tube. An exemplary construction of this is shown in FIGS. 1 and 2.

The jacket and evacuation tube is designated generally at 10 and includes a hollow can portion 11. One method of assembly includes first affixing end plate 12 to the can preferably by welding or brazing (13). Casting 5 is then placed therein. Front plate 14 having an opening 14a into which evacuation tube 15 has previously been affixed is then put in place preferably by welding or brazing. The assembly 10 including casting jacket and evacuation tube is now ready for further processing.

The evacuation procedure is carried out at a temperature from 700 to l,l00 F for a period of time of 5 to 100 hours. This removes gaseous impurities and makes the surface substantially free of such impurities. The evacuation tube is sealed off by heating the tube and then hammer welding, or other appropriate sealing. Preferably the casting is maintained under vacuum during sealing.

Alternatively, if desired, gaps can be left in the welds or brazes and the evacuation tube dispensed with. However, the surface is not as free of impurities according to this latter procedure.

In the event the metallic coating has been applied by plating, the hot evacuation step may be carried out in an evacuated chamber, or alternatively, it may be dispensed with, with some sacrifice in impurities content of the surface.

If the facilities permit it, the preferred method after heating the casting during hot evacuation is to move the hot casting with the copper jacket directly into the extrusion operation.

However, many plants would not have the facilities to do this and if this is the case, the casting may be cooled and stored. If this is the case it should then be reheated to a temperature of 700 to 1,000 F prior to extrusion. As shown in FIGS. 3-5, the extrusion die 20 may be made of conventional die materials, preferably known die steels. It is preferably rectangular and comprises a body portion 21 and shaping surfaces 22. These surfaces include radius curves 23 and an integral cone 24 for streamline flow.

The extrusion rate should be between 13 and 60 inches per minute with an amount of reduction of area of 8:1 to 24:1. In other words the ratio of inlet diameter squared to outlet diameter squared should be from about 8 to about 24. Similar principles would govern the design of dies of other casting cross sections, such as square or rectangular.

After extrusion the metal jacket is removed from the casting. This may be done by various means, for example by machining, for example on a conventional lathe of the type described above, having a tungsten carbide/cobalt or other appropriate tool. A second method involves removing the metal coating by etching or pickling, for example by placing the extrusion in an acid bath. Exemplary acids include nitric, sulphuric, halides, hydrochloric and mixtures thereof. Basic solutions may also be used, including solutions of sodium hydroxide, potassium hydroxide, ammonia hydroxide, etc. Other pickling solutions will be apparent to those skilled in the art.

After jacket removal the casting is heated for a period of 12 hours to 1 week or longer at a temperature of from 900 to 1,150 F. This heat treatment is desirable in order to relieve stresses induced during extrusion and to achieve some microstructural uniformity. The heat treatment is preferably carried out in a vacuum or an inert gas such as argon, helium or nitrogen. However, it also may be carried out in air if impurity tolerances are not too high.

After the heat treatment a rolling operation is carried out. Conventional rolls will be utilized appropriately shaped to obtain the desired product, i.e. plate or sheet, or bar or rod. The amount of reduction before annealing is about 20 to about 80%. Preferably the amount of reduction is from about 20 to 40%, before the first anneal. A reheat of 3 to 10 minutes to 900 to 1,150 F between each pass is preferably carried out. During the rolling operation the rolls are preferably at an elevated temperature, preferably at a temperature of 250 to 350 F. The roll should be lubricated with a dry lubricant for example a colloidal graphite suspension in an inert liquid carrier such as DFG sold by Miracle Powder Products Corp., Cleveland, Ohio. Rolling should be carried out from 10 to 30 mils per pass for plate thickness greater than one quarter inch and for sheet. For thin sheet this is continued until the product is 100 mils thick. For still thinner sheet reduction should be at a rate of 5 to preferably 8 to 10%. Similar adjustments should be made in processing bar (diameter above one half inch) and wire.

Next a heat treatment of 950 to l,l50 F is carried out for a period of about 20 to 40 hours.

If a uniform texture is desired in sheet or plate, after the heat treatment unidirectional rolling across the extrusion direction sufficient to balance the texture is carried out. Cross rolling is carried out with approximately a 90 directional change preferably being carried out with each pass. Between each pass there should be a reheat to a temperature of 950 to l,150 F for about 3 to 10 minutes. However, there may be two and even three passes in one direction followed by a nearly equal number of passes in a direction approximately with respect to the previous pass. Preferably the rolling is carried out at 90 change every pass. This treatment results in a balanced texture and a product having substantially uniform properties in either direction.

Sheet produced by this process may be 20 mils and thicker. Sheet and plate may be as wide and as long as equipment permits.

The resulting properties of this process include tensile strength of 50,000 to 70,000 psi, yield strength of 40,000 to 60,000 psi, and elongation of about 10 to 20%. With appropriate cross rolling of sheet and plate these properties are obtained in the transverse direction as well as the longitudinal so that the product is substantially of a balanced texture.

We claim:

1. A method of producing wrought material containing beryllium and aluminum comprising:

forming a casting of said material in a mold having high thermal conductivity material;

applying a protective metallic coating to said casting;

heating the coated casting at a temperature of 700 to 1,100 F for a period of5 to hours;

extruding the heated casting at a rate of about 13 to 60 inches per minute;

removing the jacket from the extruded casting;

heating the extrusion at a temperature of 900 to l, 1 50 F for a period of time of 12 hours to 1 week and rolling the heated extrusion at a total reduction of 10 to 2. A method according to claim 1 in which the extrusion is heated between passes during rolling.

3. A method according to claim 1 including treating said casting to remove surface imperfections and/or obtain desired shape before applying said protective coating.

4. A method according to claim 3 in which the treating operation is carried out by machining.

5. A method according to claim 1 in which coating is applied by placing said casting in a jacket.

6. A method according to claim 5 in which said jacket has an evacuation tube and said casting is evacuated during a heating step.

7. A method according to claim 1 in which the amount of production of area during extruding is from 8 to 24.

8. A method according to claim 1 in which said jacket is removed by machining.

9. A method according to claim 1 in which said jacket is removed by etching.

10. A method according to claim 1 in which the heating step prior to rolling is carried out in an inert atmosphere.

11. A method according to claim 1 in which the heating prior to rolling is carried out in a vacuum.

12. A method according to claim 1 in which the rolling step is carried out on heated rolls.

13. A method according to claim 1 in which during rolling the material is reheated between passes.

14. A method according to claim 12 in which the amount of reduction during rolling is 10 to 30 mils.

15. A method according to claim 12 in which the rolls are heated to a temperature of 250 to 350 F.

16. A method according to claim 1 in which rolling is also carried out in the transverse direction.

17. A method according to claim 1 in which below 100 mils reductions of 5 to 10 mils are taken during rolling.

18. A method according to claim 16 in which a balanced texture product is obtained.

19. A method according to claim 17 in which the wrought product obtained is sheet.

20. A method according to claim 1 in which the wrought product obtained is plate.

21. A method according to claim 1 in which the wrought product obtained is bar.

22. A method according to claim 1 in which the wrought product obtained is rod. 

2. A method according to claim 1 in which the extrusion is heated between passes during rolling.
 3. A method according to claim 1 including treating said casting to remove surface imperfections and/or obtain desired shape before applying said protective coating.
 4. A method according to claim 3 in which the treating operation is carried out by machining.
 5. A method according to claim 1 in which coating is applied by placing said casting in a jacket.
 6. A method according to claim 5 in which said jacket has an evacuation tube and said casting is evacuated during a heating step.
 7. A method according to claim 1 in which the amount of production of area during extruding is from 8 to
 24. 8. A method according to claim 1 in which said jacket is removed by machining.
 9. A method according to claim 1 in which said jacket is removed by etching.
 10. A method according to claim 1 in which the heating step prior to rolling is carried out in an inert atmosphere.
 11. A method according to claim 1 in which the heating prior to rolling is carried out in a vacuum.
 12. A method according to claim 1 in which the rolling step is carried out on heated rolls.
 13. A method according to claim 1 in which during rolling the material is reheated between passes.
 14. A method according to claim 12 in which the amount of reduction during rolling is 10 to 30 mils.
 15. A method according to claim 12 in which the rolls are heated to a temperature of 250* to 350* F.
 16. A method according to claim 1 in which rolling is also carried out in the transverse direction.
 17. A method according to claim 1 in which below 100 mils reductions of 5 to 10 mils are taken during rolling.
 18. A method according to claim 16 in which a balanced texture product is obtained.
 19. A method according to claim 17 in which the wrought product obtained is sheet.
 20. A method according to claim 1 in which the wrought product obtained is plate.
 21. A method according to claim 1 in which the wrought product obtained is bar.
 22. A method according to claim 1 in which the wrought product obtained is rod. 